In many signal amplification application, including audio amplification applications, external AC coupling capacitors are used to prevent large DC offsets. These large DC offsets can have a negative impact on chip performance. As a specific example, in audio applications these DC offsets have the negative effect of creating audible clicks and pops during startup and shutdown. Without coupling capacitors, the “click and pop” performance significantly deteriorates as the signal path gain of the audio chip increases.
While utilizing AC coupling capacitors has been a viable solution to preventing DC offsets, these capacitors have the negative effect of consuming large amounts of printed circuit board (PCB) space, increasing component cost, and degrading low frequency performance. As a point of comparison, a typical AC coupling capacitor for a typical analog chip is approximately the size of the entire chip itself.
As current audio systems grow more complex, additional AC coupling capacitors are needed. In newer audio systems the PCB space consumed by capacitors can be as high as five to ten times the PCB space consumed by the audio chip.